Image forming apparatus with curl generating means

- Canon

An image forming apparatus in which a recording medium is conveyed and held to a recording medium holding member by a plurality of conveying roller pairs, the recording medium held is conveyed to a transfer position which faces an image carrying member by a rotation of the recording medium holding member, and a visible image formed on the image carrying member is transferred onto the recording medium is disclosed. The conveying roller pair located at most downstream in the recording medium conveying direction among the plurality of conveying roller pairs are constructed so as to selectively perform rotation/stop of rollers and contact/separation of a nip. At least one of the other conveying roller pairs are constructed so as to selectively perform rotation/stop of the rollers.

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Claims

1. An image forming apparatus in which a recording medium is conveyed to a recording medium holding member by a plurality of conveying means, the recording medium held by said recording medium holding member is conveyed to a transfer position which faces an image carrying member by a rotation of said recording medium holding member, and a visible image formed on the image carrying member is transferred onto the recording medium, wherein the image forming apparatus includes,

a first conveying means from among said plurality of conveying means having a conveying roller pair, which is located at a most downstream position of said plurality of said conveying means in a conveying direction of the recording medium;
means for selectively performing rotation/stop of said conveying roller pair and contact/separation of a nip formed by said conveying roller pair;
a second conveying means of said plurality of conveying means;
means for selectively executing rotation/stop of said second conveying means of said plurality of conveying means, said second conveying means having curling conveying rollers for giving a curl to the recording medium in a recording medium wrapping direction of said recording medium holding member.

2. An apparatus according to claim 1, wherein a front edge portion of the recording medium after having passed through said curling conveying rollers is abutted downstream thereof and a loop shape formed on the abutted recording medium corresponds to the curling direction given by said curling conveying rollers.

3. An apparatus according to claim 2, wherein the conveyance of the recording medium by said plurality of conveying means is started at a time when a loop amount by the curl of the recording medium which have collided on a downstream side than said curling conveying rollers, is equal to or less than 3 mm.

4. An image recording apparatus comprising:

conveying means for feeding out a sheet medium supplied from a paper feed section to a registration portion through a paper path having a curved portion;
image forming means for forming an image on the fed sheet medium;
registration means for forming a loop space by once stopping a front edge of the sheet medium in order to correct an oblique movement of the sheet medium, and for feeding out the sheet medium to said image forming means; and
a drum arranged downstream of said registration means in a sheet medium conveying direction for holding the sheet medium and conveying the sheet medium to said image forming means,
wherein guide members for forming an outside of said paper path curved portion are moveable and the loop space is formed by a movement of at least one of said guide members, wherein at least one of said movable guide members is constructed so that movements of both edges in a paper width direction are independently executed.

5. An apparatus according to claim 4, further comprising a curling mechanism for giving a curled shape to the sheet medium in a direction along the drum, said curling mechanism provided on an upperstream side in the sheet medium conveying direction of the paper path curved portion in said conveying means.

6. An image forming apparatus comprising:

a rotating body by which a sheet is wound in a direction around a curved surface thereof and held;
image forming means for forming an image on the sheet held by said rotating body;
a conveyance path for guiding the sheet to said rotating body; and
curl giving means provided in said conveyance path and for giving a curl to the sheet in the direction in which the sheet is wound around the curved surface of said rotating body; and
oblique movement correcting means provided in said conveyance path and for curving the sheet with once stopping a front edge of the sheet in order to correct an oblique movement of the sheet being conveyed.

7. An apparatus according to claim 6, wherein said oblique movement correcting means curves the sheet in the direction in which said sheet is wound around the curved surface of said rotating body.

8. An apparatus according to claim 7, wherein said curl giving means functions as said oblique movement correcting means for once stopping the front edge of the sheet being conveyed.

9. An apparatus according to claim 7, wherein said oblique movement correcting means is provided one downstream side of said curl giving means in a sheet conveying direction.

10. An image forming apparatus according to claim 6, wherein said curl giving means comprises a primary roller and first and second secondary rollers for curling the sheet as it passes through said conveyance path, and whereafter the sheet continues through said conveyance path in a non-curled state but returns to a curled state when it is wound around the curved surface of said rotating body.

11. An image forming apparatus according to claim 10, wherein said primary roller is metal and said secondary rollers are made of an elastic member.

12. A sheet conveying apparatus, comprising:

conveying means for conveying a sheet;
oblique movement correcting means for correcting an oblique movement of the sheet by curving the sheet in a direction with once stopping a front edge of the sheet conveyed by said conveying means; and
a guide member moveable with being pushed by the sheet curved by said oblique movement correcting means, said guide member being adapted so that movements of both edges in a sheet width direction are independently executed.

13. An apparatus according to claim 12, wherein said conveying means conveys the sheet along a conveyance path including a curved portion, and the sheet is further curved by said oblique movement correcting means in the direction of said curved portion.

14. An apparatus according to claim 13, further comprising curl giving means for giving a curl to the sheet being conveyed along said conveyance path in a direction opposite to said curve direction of said curved portion.

15. A sheet conveying apparatus, comprising:

conveying means for conveying a sheet;
oblique movement correcting means for correcting an oblique movement of the sheet by curving the sheet in a direction with once stopping a front edge of the sheet conveyed by said conveying means;
a first guide member moveable with being pushed by the sheet curved by said oblique movement correcting means; and
a second guide member provided downstream of said first guide member in a sheet conveying direction and moveable with being pushed by the sheet curved by said oblique movement correcting means.

16. An apparatus according to claim 15, wherein said first guide member swings around a pivot at its upstream side, and said second guide member swings around a pivot at its downstream side.

17. An apparatus according to claim 15, wherein said conveying means conveys the sheet along a conveyance path including a curved portion, and the sheet is further curved by said oblique movement correcting means in the direction of said curved portion.

18. An apparatus according to claim 17, further comprising curl giving means for giving a curl to the sheet being conveyed along said conveyance path in a direction opposite to the direction of said curved portion.

19. An image forming apparatus, comprising:

a rotating body by which a sheet is wound in a direction around a curved surface thereof and held;
image forming means for forming an image on the sheet held by said rotating body;
means for defining a conveyance path for guiding the sheet to said rotating body; and
curl giving means provided in said conveyance path defining means and for giving a curl to the sheet in the direction in which the sheet is wound around the curved surface of said rotating body, wherein said curl giving means comprises a primary roller and first and second secondary rollers for curling the sheet as it passes through said conveyance path defining means, and whereafter the sheet continues through said conveyance path in a non-curled state but returns to a curled state when it is wound around the curved surface of said rotating body.

20. An image forming apparatus according to claim 19, wherein said primary roller is metal and said secondary rollers are made of an elastic member.

21. An image forming apparatus, comprising:

convey means for conveying a sheet;
a pair of registration rollers for conveying the sheet, said registration roller pair temporally holding a tip end of the sheet conveyed by said convey means to bend the sheet for correcting a skew-feed thereof;
a guide member shiftable by pressing from the sheet bent by said registration roller pair, both end portions of said guide member in a sheet widthwise direction capable of shifting independently; and
image forming means for forming an image on the sheet the skew-feed of which is corrected by said registration roller pair.

22. An image forming apparatus, comprising:

convey means for conveying a sheet;
a pair of registration rollers for conveying the sheet, said registration roller pair temporally holding a tip end of the sheet conveyed by said convey means to bend the sheet and form a loop portion for correcting a skew-feed thereof;
a first guide member shiftable by pressing from the loop portion of the sheet bent by said registration roller pair;
a second guide member disposed down-stream of said first guide member in a sheet convey direction and shiftable by pressing from the sheet bent by said registration roller pair; and
an image forming means for forming an image on the sheet the skew-feed of which is corrected by said registration roller pair.

23. An image forming method in which a sheet is held on a hold means, then the hold means is rotated to transfer an image of an image bearing member onto the sheet at a transfer position for the image formation, comprising steps of:

correcting a skew-feed of the sheet by causing a tip end of the sheet to abut against a nip of a stopped pair of curl applying convey rollers, and forming a curl on the sheet in a direction surrounding the hold means by rotating the curl applying convey rollers;
forming a loop on the sheet by holding the tip end of sheet to which the curl is applied by the nip of a registration roller pair;
conveying the sheet to the hold means by rotating the registration roller pair; and
separating one roller of the registration roller pair after the sheet tip end reaches the hold means.
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Patent History
Patent number: 5933697
Type: Grant
Filed: Jan 8, 1997
Date of Patent: Aug 3, 1999
Assignee: Canon Kabushiki Kaisha (Tokyo)
Inventors: Shinichi Onodera (Tokyo), Kunihiko Matsuzawa (Kawasaki)
Primary Examiner: William J. Royer
Assistant Examiner: Sophia S. Chen
Law Firm: Fitzpatrick, Cella, Harper & Scinto
Application Number: 8/780,716